package homework.hw3;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;

/**
 * @Author Administrator
 * @Date 2020/5/22 10:07
 **/
@WebServlet("/downLoad")
public class DownLoad extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /*1.得到文件名filename：通过获取请求参数
        2.得到文件的真实路径realPath：通过ServletContext
        3.通过字节输出流读取真实路径下的文件
        4.以附件的形式下载文件，需要设置响应头
        response.setHeader("Content-Disposition","attachment;filename="+filename);
        5.通过输入流读取文件，输出流写数据*/
        String filename = req.getParameter("filename");
        System.out.println(filename);
        ServletContext servletContext = req.getServletContext();
        String realPath = req.getServletContext().getRealPath("/img/"+filename);
        FileInputStream fis=new FileInputStream(realPath);
        /*当文件名是中文名时，若要下载后的文件名跟原始文件名一致
        * 当需要考虑不同浏览器对中文名编码utf-8是不一样的*/
        String agent = req.getHeader("User-Agent");
        //filename = DownLoadUtils.getFileName(agent,filename);
        resp.setHeader("Content-Disposition","attachment;filename=" + filename);
        ServletOutputStream outputStream = resp.getOutputStream();
        byte[] bytes=new byte[1024];
        int len=0;
        while ((len=fis.read(bytes))!=-1){
            outputStream.write(bytes,0,len);
        }
        fis.close();
        outputStream.close();

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}
